1. Field of the Invention
This invention relates to a commutator, and more particularly to a flat disk commutator in which a segment is arranged on one end face in axial direction of a boss and in a circumferential direction of the boss, which is effectively employed, for instance, in an "In-Tank Type Fuel Feed Pump" in which a motor is integrated with a pump.
2. Related Art Statement
In general, as a fuel feed pump for feeding a fuel to a vehicle such as an automobile, an "In-Tank Type Fuel Feed Pump" in which a motor is integrated with a pump, which is provided in a fuel tank, has been proposed. In an "In-Tank Type Fuel Feed Pump", a "Flat Disk Type Commutator" is employed as a motor.
One the other hand, an "In-Tank Type Fuel Feed Pump" is generally constructed so that a fuel can be fed from a pump to the outside through a motor housing. In this case, the fuel touches to the commutator of the motor.
By the way, in the case of use of gasohol in which alcohol is mixed with the gasoline as fuel, when copper of the commutator which is used in the motor of the fuel feed pump contacts with the gasohol, the fuel is altered, or the copper is penetrated. Hence, a commutator for gasohol is proposed in, for example, U.S. Pat. No. 5,175,463. In this patent, a protecting portion chip(s) made from carbon is(are) attached, by soldering, to at least one surface contacting a brush in a copper of a base member of a segment (commutator bar). In this commutator, carbon has almost no solderability, so that a nickeling and a coppering for a soldered face of the protecting portion chip made from carbon is proposed.
However, in the commutator in accordance with the prior art, a plating step is necessary, so that the manufacturing steps and the manufacturing costs increase.
Further, the protecting portion chip made from carbon by soldering is electrically and mechanically connected to a base material of the segment, so that there is a possibility that the soldering layer could melt and escape from a connecting surface between the carbon protecting portion chip and the base material of the segment when an armature coil is fused to the riser portion protrudely integrated with the base material. High fusing point solder is therefore used to avoid this state, operating time for the soldering become long, so that the productivity even more decreases.